As the scandal spread to more processors, the fraud squad has been called in to help agriculture authorities track down the source of the mislabelled meat.

"This is a matter of reputation, obviously we cannot afford to have that," Mr Kenny said.

"It is a matter that needs to be sorted out and it will be sorted out."

Rangeland Foods in Co Monaghan was one of the latest plants shut down after a sample at the factory tested positive with a reading of 75% horse DNA in raw ingredient, authorities said.

It supplies burgers to one of Ireland's most popular fast food chains, Supermacs, but the restaurant's chief executive Pat McDonagh has insisted he is sure all his burgers are 100% Irish.

The highest level of horse has been found in a quantity of frozen meat being stored in the North.

Freeza Meats in Newry had meat which was 80% horse, which the UK's Food Standards Agency (FSA) said was potentially linked to the Silvercrest factory in the Republic of Ireland, one of the first processors to be named in the scandal.

The meat has not entered the food chain.

The same meat trader in Ireland has supplied meat to Freeza, Silvercrest and Rangeland, the Food Safety Authority of Ireland (FSAI) said.

The source has been blamed on a meat supplier in Poland.

Professor Alan Reilly, whose research at the FSAI first exposed the contamination of processed beef burgers in Irish-made products, is due to brief a parliamentary committee on the controversy this afternoon.

"The net is tightening for sure but the investigations have some way to go," Prof Reilly said.

"We are no longer talking about trace amounts... We are talking about horse meat. Somebody, some place is drip-feeding horsemeat into the burger manufacturing industry. We don't know exactly where this is happening."

All checks by Irish and UK authorities have shown the contaminated or mislabelled meat has come from Poland, either directly, or through traders in the UK or one trader in Ireland.

However, Mr Kenny said he was expecting a briefing at Cabinet today and also suggested that allegations an Irish supplier was involved in using contaminated meat would be examined.

Agriculture Minister Simon Coveney will also brief a parliamentary committee on the horse meat controversy this afternoon after the positive tests at Rangeland.

Irish Farmers' Association (IFA) president John Bryan said the deepening scandal was further evidence that only Irish raw material must be used in the manufacture of Irish beefburgers.

“It is clear that stricter controls must apply to the secondary processing industry, particularly where imported products are being used,” he said.

In a statement, Freeza Meats insisted all its own finished products, including burgers, have tested negative for horse meat and equine DNA.

“All tests that have been carried out routinely on our own finished products (ie burgers) have been negative. There have been no traces of equine DNA in any samples taken from Freeza Meats products,” a spokesman said.

Freeza meats said the positive test for horse meat came from samples from a parcel of raw material being held in storage for a meat trader based in Ireland.

The company said it kept the meat on its premises out of goodwill in a “separated area of the storage facility”.

“This raw material was not purchased by Freeza Meats and never reached the food chain through this company,” a spokesman said.

“We have under legal jurisdiction been required to detain the product in quarantine awaiting the direction of the local Environmental Health Office.”

Freeza Meats said food safety chiefs in Northern Ireland have always been aware of the background of the contaminated parcel.

It was first identified by authorities in September and put into quarantine.

The company employs more than 45 people and has been in business since 1988.

“We are fully committed to working with our suppliers and customers. Given the sensitivities of the area in which we work, jobs could be put unnecessarily at risk by misinformation. We look forward to working with the relevant agencies in Northern Ireland to resolve this issue,” a spokesman said.

Meanwhile, Irish authorities have been examining the role Irish traders may have played.

McAdam Foods, a meat trader based in Co Monaghan, confirmed a team of special investigators from the Department of Agriculture had been inspecting its premises and its deals with Polish suppliers.

A spokesman for McAdam Foods said: “We are complying fully with the Department of Agriculture, Fisheries and Food.

“A special investigations team have been here this morning and we have given them sufficient information at this point regarding our suppliers in Poland.”